Conventional commercial and military satellite communications applications require a high downlink effective isotropic radiated power (EIRP) and a high uplink gain/temperature ratio (G/T) to close the communications link between, for example, a satellite and a ground station. These higher downlink and uplink requirements require the use of a high gain antenna system, which in turn results in smaller beam size. For cellular earth field of view (EFOV) coverage, a multi-beam antenna system must be utilized in which the antenna provides a beam scan capability of up to 15 beamwidths away from the antenna boresight with low scan loss and minimal beam distortion. Multiple aperture reflector antenna systems with interleaved beams, or a single aperture reflector antenna system using shared feeds to generate contiguous earth coverage beams, are typically deployed.
However, the multiple aperture reflector antenna systems require a significant amount of hardware and complex spacecraft packaging that result in a high overall system cost. A single aperture reflector antenna system with shared feeds also is expensive, as the beam-forming network that must be used due to the fact that each of the feeds is shared by more than one beam is highly complex. In addition, such a system has a high associated beam-forming network loss and relatively large overall weight.
Therefore, it is an object of the present invention to provide a multi-beam satellite antenna system with a single aperture shaped reflector that optimizes beam crossover and overall system size, cost and complexity.
It is another object of the present invention to provide a single aperture side-fed dual reflector antenna system that generates substantially contiguous flat beams, each of which provides substantially uniform coverage within a predetermined coverage area on the terrestrial target.